I don't know but let's do a little accounting because as mad as it sounds 50m may be too little.
Firstly losing Alexis probably means losing another season of CL footie meaning about 50m of less revenue. It also means we definitely finish behind you, decreasing our CL chances further.
But let's value a year of Alexis playing that aside. He'd probably be 150m player in the insane market on a long term deal if he was young, right? I mean Countinho's probably costing 120m, Mbappe isn't as proven but may have a higher ceiling and is priced around that. Supposedly Alexis wants 400k a week, so that's something like 21m a year.
So losing 50m for his prime year and 7m a year in wages is actually not too bad value. It's only a bit over twice as much as his wages on 400k a week and is he worth 30m per year in transfer fee in the current market? He possibly is. Especially if he plays his socks off to earn his next big deal.
It depends how Wenger values him and what his contingency plan is. I'd imagine Wenger would want cash left over after buying Lemar who's currently valued at 70m-80m. 50m doesn't cover that. Wenger generally never sells his best players for 1/4 of the world record fee, 1/2 sure, Anelka/Fabregas. Even 1/3 with RVP but never a 1/4. Even Nasri and Adebeyor went for 1/3 of the world record and they weren't our best player. For the record though Wenger didn't want to sell Nasri/RVP he wanted them to play out their final year but the money got for them is better than 50m today.
Now I do think Alexis is probably on strike right now, but if he's forced to stay and honour his contract he'll play well to get the best contract he can.
Also, keeping Alexis doesn't guarantee CL as we saw last season.
I do think it's bad value because Alexis can suffer a major injury and there is too much risk involved. This is why Pogba was sold last summer and Mbappe will most likely be sold this summer, keeping them could result in better value next summer but they run the risk of a loss of form or major injury that could decrease value.
Wenger has a lot of power but he doesn't make all the decisions, he is a puppet. Ultimately Kroenke and the board will decide if Alexis is sold or not. I'm not buying this 1/2, 1/3 the world record talk. Nobody is paying 80-100m for a player in the last year of their contract as good as they are.
Kroenke will be looking at this situation from a business point of view. They didn't get CL with him. Keeping him means constant media speculation about his future further damaging team morale. Keeping him means losing 50m+, wouldn't even be surprised if City pay close to 60m. Sanchez gives you a better chance for CL football but the cons far outweigh the pros for keeping him.
Add to that Ozil & Ox in similar situations, that's 100m+ in transfer fees. From a business point of view the best thing would be to sell all 3, reinvest the money in two class players and go from there. It doesn't look like any of them will sign a new deal.
No player is bigger than a club. Players get sold, new ones get bought and fans move on. If Sergio was in the same situation and wanted out I would hope City would sell him and not force him to stay, only to lose him on a free, makes no sense at all. Especially when you consider he could easily still end up going to a rival.
It's pretty obvious Sanchez is making his intentions clear. City have not bid yet and it's not even necessary to bid yet as the end of the window nears our postion gets stronger. City will probably make a bid in a week or two , the press will be briefed about it, 40m maybe. Arsenal will reject it immediately, Sanchez will put in a transfer request and he will get sold near the end of the window. This is how I see it playing out. Arsenal and Wenger will claim they had no choice but to sell, Sanchez will be public enemy #1, and everyone is happy. Sanchez will get booed often but he won't care as he smiles and waves to the City fans while he lifts the PL trophy.
FWIW I think Arsenal can sell Sanchez, buy Lemar and maybe one more player or two. Your new left back looks great and is perfect for the PL. With spurs having wembely, rags not improving much, Liverpool as well and Chelsea having such a thin squad, I would say Arsenal have a great chance of making top 4. Sell the players that want out, buy ones that want to give everything for the badge and you'll be better off.